The shock and vibrational characteristics of ball bats have been studied by people in the arts of sports engineering and mechanical engineering. When a ball bat strikes a ball or another object, the impact causes waves of vibration that correspond to various bending modes of the ball bat. Each mode of vibration includes one or more nodes and antinodes. Nodes are generally understood to be the points along the length of the ball bat where the amplitude of a wave in a particular mode is zero. Accordingly, a node corresponds to a location of minimal or zero vibration. An antinode is generally understood to be a point along the length of the ball bat where the amplitude of a wave in a particular mode is at its maximum. Accordingly, an antinode corresponds to a location of maximum shock or vibration. In ball bats, players typically sense vibration according to the first and second bending modes, with the most sensation typically associated with the second bending mode. Vibration and shock in a ball bat can cause a player discomfort or injury.
Some ball bats are made in two or more pieces. Two-piece ball bats are typically constructed by joining a barrel section to a handle section. Existing two-piece ball bats exhibit a small amount of flex between the barrel section and the handle section during impact with a ball. This flex may contribute to an increase in bat speed due to an increased whip effect but may decrease overall performance due to energy lost when the bat flexes. Flex in the interface between the barrel section and the handle section of existing two-piece bats may reduce shock to a user's hands and increase player comfort to some extent, but existing two-piece ball bats do not have optimal shock-attenuating characteristics.